The present invention relates generally to orthopedic surgical procedures, most particularly for use in fixation of the spine. More particularly, the present invention relates to a system for anteriorly fixating the cervical spine. The present invention also pertains to a related method of withdrawing a bone screw from a plate.
In certain orthopedic surgical procedures, it is necessary to secure multiple bones or bone portions relative to each other. For example, in spinal surgeries, the fusion of two or more vertebrae bodies is required to secure a portion of the spinal column in a desired position. This need may be the result of physical trauma from fractures or dislocations, degenerative diseases, or tumors.
One such spinal fixation procedure involves the attachment of a prosthesis or plate to the anterior side of the cervical portion of the spine. The procedure requires anteriorly accessing the spine and securing a prosthetic plate to the one or more cervical vertebrae. This allows fusion of the one or more cervical vertebrae in a particular orientation so to facilitate healing or to repair a condition of the patient.
Various fusion plates and plating systems are known for anteriorly fusing the cervical spine. While known anterior plating systems have addressed certain requirements associated with the surgical repair of bone, in general, and spinal fusion, particularly, all are associated with limitations. The requirements associated with spinal stability and system reliability over an extended period of use often conflict with the requirements of an easy to use implant. For example, strength requirements for a fusion plate tend to make the plate bulky and adversely effect intra-operative and postoperative viewing of the associate area of the spine. In this regard, the affected region of the cervical spine cannot be easily viewed using MRI or x-ray procedures to verify that the desired fusion of the cervical spine is complete and/or that the alignment of the cervical vertebrae is proper.
Additionally, ensuring that bone screws do not loosen over time or back out from the plate tends to complicate implantation of known anterior plating systems. Known locking mechanisms generally ensure that the bone screws placed into the vertebrae through the plating system do not loosen or back out from the plate. When a locking mechanism has been included with known anterior cervical plating systems, it generally incorporates a discrete fastener or other element. As such, an additional surgical step is required. Furthermore, known locking mechanisms do not adequately permit the removal of an associated bone screw when required.
Furthermore, known plating systems often do not permit sufficient angular freedom for bone screws relative to a plate. Generally, known plating systems have defined bores through which bone screws are placed at a predefined angle. Therefore, the operating surgeon often does not have freedom to insert the bone screws into the vertebrae as to best fit the anatomy of the individual patient. While some known systems do permit bone screw angulation, they typically are not adapted to be used with an easy to use locking mechanism.
It remains desirable in the pertinent art to provide an anterior cervical plating system that addresses the limitations associated with known systems, including but not limited to those limitations discussed above.
The present invention relates to plating systems for the fixation of the cervical spine. In particular, the present invention relates to an anteriorly placed plating system for a cervical portion of the spine. According to one aspect, the present invention relates to a locking mechanism for preventing the withdrawal of locking bone screws from a plate after being implanted. The locking mechanism is integral to the plating system and does not require the additional insertion of additional fasteners or other discrete members into the plate after the bone screws have been fastened to the spine. The locking mechanism preferably allows for angular freedom of the bone screws as they are inserted through the plate.
In another aspect, the present invention relates to a plate member of a cervical plating system that permits enhanced viewing of an adjacent portion of the spine area intra-operatively and post-operatively. the plate member includes a first pair of nodes having a first node and a second node defining first and second bone screw apertures, respectively. The first and second nodes are at least partially circular in shape and spaced apart from one another in a first direction. The plate member additionally includes a second pair of nodes having a third node and a fourth node defining third and fourth bone screw apertures, respectively. The third and fourth nodes are at least partially circular in shape and spaced apart from one another in the first direction. The plate member further includes a first plurality of linking segments extending in a second direction substantially perpendicular to the first direction and connecting the first and second pairs of nodes. Adjacent linking segments define elongated viewing windows.
In a further aspect, the present invention relates to a method of surgically repairing bone with an elongated plate having a plurality of bone screw apertures. The method includes the step of locating a locking ring in one of the bone screw apertures. The locking ring defines a locking ring opening and is resiliently expandable from a retracted state to an expanded state such that the locking ring opening has a first opening diameter in the retracted state and a second, larger diameter in the expanded state. The method additionally includes the step of removing the bone screw from the one bone screw aperture with a tool having a first portion engaging the head of the bone screw and a second portion resiliently expanding the locking ring to the expanded state.
In yet another aspect, the present invention relates to a system for surgically repairing bone. The system includes an elongated plate having a plurality of bone screw apertures. A locking ring is disposed in one of the bone screw apertures. The locking ring defines a locking ring opening and is resiliently expandable from a retracted state to an expanded state such that the locking ring opening has a first opening diameter in the retracted state and a second, larger diameter in the expanded state. A bone screw is inserted into the one of the bone screw apertures. The bone screw has a head with a diameter greater than the first opening diameter and less than the second opening diameter. The system further includes a tool for removing the bone screw from the one bone screw aperture. The tool has a first portion engaging the head of the bone screw and a second portion for resiliently expanding the locking ring to the expanded state.
An advantage of the present invention is to provide an anterior cervical plating system that provides a locking mechanism including a pre-attached locking ring, thereby eliminating the need for discrete locking components.
Another advantage of the present invention is to provide an anterior cervical plating system with an integral locking mechanism that maintains a low profile and thereby minimizes interferences with anatomical soft tissue structure.
Another advantage of the present invention is to provide an anterior cervical plating system that provides a plate having an open design permitting intra-operative visualization of bone grafts and vertebrae end plates, as well as post-operative visualization of bone graft consolidation and spinal orientation on an anterior/posterior x-ray.
Another advantage of the present invention is to provide an anterior cervical plating system that provides a variable angle bone screw permitting approximately 20xc2x0 of screw angulation.
Another advantage of the present invention is to provide a cervical plating system including a predefined angle. Therefore, the plate need not be manually fashioned to fit the spine thereby decreasing surgical time and interference with soft tissue after implantation.
Additional advantages and further areas of applicability of the present invention will become apparent from the following detailed description and appended claims. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.